Guru, you're right, of course, but I respectfully submit that more animals have been wounded by such mismatched equipment than killed cleanly. Shot placement is #1, but you have to be somewhere close to tuned to get shot placement. You have to be tuned to hit where you aim, or you just trust to luck. Trusting to luck is the best way to miss or wound.
Nightowl, you can't really separate the items on your list from each other or ignore any of them- they're mutually dependent. Skimp on any of them and your performance on game (or targets) will suffer. There are hundreds of possible combinations of the items on the list that will work, but only in concert with each other.